REST API Interview Questions and Answers

Rest API Interview Questions

What is REST API?

REST API is a type of web service that allows different software systems to communicate with each other using HTTP(S) requests and responses. In a RESTful architecture, data and functionality are treated as resources that can be accessed and manipulated using standard HTTP methods, such as GET, POST, PUT, and DELETE.

Quick Questions about REST API

REST API full formRepresentational State Transfer, Application Programming Interface
REST API is aSoftware Architectural Style
REST API is also known asRESTful API
REST API is used forCreating mobile & web-based applications, Integrating different systems

Key Responsibilities of REST API Developer

As a REST API developer, some of the key responsibilities you may be expected to have include:

  • Designing and implementing RESTful APIs.
  • Developing API documentation.
  • Testing and debugging APIs.
  • Collaborating with other developers.
  • Ensuring API security.
  • Monitoring API performance.
  • Keeping up to date with industry trends
Download Rest API Interview Questions PDF

Below are the list of Best Rest API Interview Questions and Answers

REST, expanded as Representational State Transfer, is an architectural style developed by Roy Fielding in 2000. REST presents a set of constraints to be used in the creation of web services. The services that use REST constraints are called as RESTful Web Services. For an interface to be referred to as RESTful, it should satisfy the six-guiding constraints. These constraints are names as the client-server, stateless, cacheable, uniform interface, layered system, and code on demand.

After satisfying the constraints, the RESTful web services can be used to provide an interface between the computer system and the internet. Using this interface, a system can access and manipulate the resources present on the web by using a predefined set of operations.

In the REST architecture, every content is a resource. It can be a text file, HTML pages, images, videos, or business data. These resources are identified by the URI or global ID’s which can be used by the REST client to access or modify.

The most used representation of the resources is XML and JSON. Resources can also be grouped into a collection of the same type.

The options the REST are annotations that are used to indicate whether a method responds to the HTTP OPTIONS request only. It allows the client of the REST API to determine what HTTP methods (GET, HEAD, POST, PUT, DELETE) can be used for the resource identified by the requested URI. The client determines without initiating a resource request.

The REST OPTIONS method is also used for the CORS (Cross-Origin Resource Sharing) request.

URI (Uniform Resource Identifiers) is used to identify each resource in the REST. An HTTP operation is called by the client application to access the resource. In the construction of a URI to identify a resource, some rules are to be followed. The resource should be defined in the plural noun. The URI is case0sensitive, so use a lowercase letter when defining a URI. There should be no spaces included in the URI. The created URI should be backward compatible.

//FORMAT for creating a URI


The payload is used by the REST API to pass and return data structures. It is used when the data is too large to be passed as a parameter. The input payload is a filter definition passed in the request to test result resources. The output payload is a set of test results. Payloads have a predefined structure to easily create, consume, manipulate and present by the client tools.

REST supports a group of HTTP methods to manipulate the request and response. They are,

GET – It is used to read the representation of a resource. It usually returns the resource in XML or JSON type with the HTTP response code 200 on successful creation.

POST – It is used to create new resources. It is usually used to create a subordinate resource and returns HTTP code 201 on successful creation.

PUT – This method mainly used to update the resource. It can also be used to create a resource when the resource ID is selected by the client. It returns response code 200 on a successful update.

PATCH – It is used to modify the resource. It only contains the change needed to be modified in the resource.

DELETE – It deletes a resource. The resource needed to be deleted is identified by a URI. It returns an HTTP status 200 on successful completion.

AJAX (Asynchronous JavaScript and XML) is a set of technologies, that are used for updating the data and web page without reloading the page. Using this, you can send data in the background, and request/receive data from a server after the page has loaded.

REST (REpresentational State Transfer) uses HTTP requests to transfer data between the client and the server. It defines a set of constraints for the successful creation of RESTful web services.

AJAX and REST are completely orthogonal. You can use REST for creating an AJAX call. REST is one way of implementing AJAX.

Postman is a popular test and development tool to simplify the API workflow. It provides the tool to manage every stage of the API lifecycle and makes the development of the API simple.

With postman, you can design, debug, test, document, monitor, and publish the API from one place. It also provides version control and tagging to maintain multiple versions of the API. It also provides a testing tool to automate the testing process.

Postman can also be used to create a mock server to simulate the endpoints and the response.

SOAP (Simple Object Access Protocol) is used to exchange data between different platforms easily. It has a specification and WSDL file that has information about the location and function of the web service. It uses a service interface to expose its functionality to the clients.

REST is an architectural style pattern to create a RESTful web service. It uses normal HTTP requests to receive/request the resource on the web. REST uses SOAP as an underlying protocol for the creation of web services as it is just an architectural design.

The data in the RESTful web service is mainly represented in XML or JSON form.

XML (Extensible Markup Language) is used to store and transfer data.

JSON (JavaScript Object Notation) is used to serialize and transfer data. It is lighter than XML and can transfer the same amount of data as the XML with less bandwidth.

The status code in the REST API is divided into five categories. They are,

1xx – It is used to communicate the transfer protocol-level information.

2xx – It is used to indicate the request was accepted successfully. Some codes are,

  • 200 (OK) - It indicates the request is successfully carried out.
  • 201 (Created) - It is returned when a resource is created inside the collection.
  • 202 (Accepted) - It indicates the request has been accepted for processing.
  • 204 (No Content) - It indicates when a request is declined.

3xx – It indicates the client must take additional action to complete the request.

4xx – It is the client error status code.

5xx – It is the server error status code.

A stateless server is a server that keeps no state information and stateless file servers do not store any session state. Therefore, every client request is treated independently, and not as a part of a new or existing session. A stateless server does not need a client to first establish a connection to the server. So, it views a client request as an independent transaction and responds to it.

Google App Engine (GAE / App Engine) in Google Cloud Platform is a Platform as a Service (PaaS) for developing and hosting web applications in Google-managed data centers. Applications are sandboxed and operated via multiple servers and an app engine allows automatic scaling for web applications as the number of requests progress for an application, it automatically allocates more resources for the web application to manage the additional demand.